From 8f6055cbaf68cbd9ff2692a2cfa691b43629ccd4 Mon Sep 17 00:00:00 2001 From: Joerg Roedel Date: Fri, 25 Mar 2011 09:44:48 +0100 Subject: [PATCH] KVM: X86: Make tsc_delta calculation a function of guest tsc The calculation of the tsc_delta value to ensure a forward-going tsc for the guest is a function of the host-tsc. This works as long as the guests tsc_khz is equal to the hosts tsc_khz. With tsc-scaling hardware support this is not longer true and the tsc_delta needs to be calculated using guest_tsc values. Signed-off-by: Joerg Roedel Signed-off-by: Avi Kivity --- arch/x86/kvm/x86.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 78d7291..fcce29b 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2113,8 +2113,13 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) kvm_x86_ops->vcpu_load(vcpu, cpu); if (unlikely(vcpu->cpu != cpu) || check_tsc_unstable()) { /* Make sure TSC doesn't go backwards */ - s64 tsc_delta = !vcpu->arch.last_host_tsc ? 0 : - native_read_tsc() - vcpu->arch.last_host_tsc; + s64 tsc_delta; + u64 tsc; + + kvm_get_msr(vcpu, MSR_IA32_TSC, &tsc); + tsc_delta = !vcpu->arch.last_guest_tsc ? 0 : + tsc - vcpu->arch.last_guest_tsc; + if (tsc_delta < 0) mark_tsc_unstable("KVM discovered backwards TSC"); if (check_tsc_unstable()) { -- 2.7.4